Before diving into the specifics of the MC801A, it is important to understand what firmware is. Unlike standard software or apps that you install and delete on a whim, firmware is a specific class of computer software that provides the low-level control for the device's specific hardware. It is the operating system that tells your router how to communicate with the cellular tower, how to manage Wi-Fi bands, and how to prioritize data traffic.
The easiest way to keep your router current is through the built-in management interface: zte mc801a firmware